1. Field of the Invention
The present invention relates to a server for handling output units by receiving a job request to the output units from a client.
2. Description of the Related Arts
As electronic units such as a computer have become smaller both in size and weight, a configuration in which a plurality of clients share output units connected to a server has become popular. In such a configuration, the output units including a printer, a facsimile, a plotter, and an electronic black board are connected to a server, and a client uses these output units by sending a job request to-the server. Parallel with this configuration, another configuration in which the client uses output units connected to another server when it is reconnected thereto due to a change in its physical location has also become popular.
FIG. 1 depicts the construction of a system for conventional server as an example, and the explanation thereof will be given in the following. In the drawing, the output units, a printer 2 and a facsimile 3, are connected to a server 1 while a printer 5, a facsimile 6, and a plotter 7 to a server 4. A client 8 is initially connected to the server 1. Given these circumstances, the client 8 sends a job request to a printer control process 9 or a facsimile control process 10 installed in the server 1 to use the printer 2 or facsimile 3, respectively. Note that the job request to the printer control process 9 and that to the facsimile control process 10 are formatted differently.
Next, assume that the client 8 has changed its physical location, and is now connected to the server 4 for reasons of convenience such as a distance. Then, the client 8 sends a job request to a printer control process 11, a facsimile control process 12, or a plotter control process 13 installed in the server 4 to use the printer 5, facsimile 6, or plotter 7, respectively. Note that the job requests to the printer control process 11, facsimile control process 12, and plotter control process 13 are all formatted differently.
However, the above described conventional system has the following five problems:
(1) Because different servers require different procedures and data formats for both the same and different types of output units, a user must check the proper procedure and data format of an output unit connected to another server and convert the data format accordingly when the client is reconnected to that server due to a change in physical location or loading limit. For example, in the case shown in FIG. 1, where the client 8 is reconnected to the server 4 from the server 1, the client 8 sends a job request to the printer control process 11 to use the printer 5. However, the printer control process 9 of the server 1 and the printer control process 11 of the server 2 operate on different data formats. Thus, the user must check the procedure and data format of the printer control process 11 and convert the data format at the client 8. Assuming that a UNIX operating system is applied, then, a daemon process called "lpd" is responsible for the printer control processes 9, 11, and a printer and a printout format are specified by an entry written in a file called "printcap"; however, each server uses different entries. Hence, an entry that specifies the printer 2 of the server 1 does not specify the printer 5 of the server 4. Therefore, the user must check the entry for the printer 5 to either specify the entry or convert the data format at the client 8. PA0 2) The user must input information of output units connected to a server each time the client is reconnected; for no technique such that automatically provides the information of the output units has been developed yet. For example, when the client 8 is reconnected to the server 4 from server 1, the client 8 will not have any information of the plotter 7 unless the user inputs it. PA0 3) Different types of output units operate on different procedures and data formats even when they all are connected to one server. For this reason, the user must convert a job request to the printer control process 9 in one data format, and to the facsimile control process 10 in another format at the client 8, which complicates the operation of the client 8. PA0 4) It is time-consuming to operate the conventional system. Because the user must input a data-output command in a specific data format for each output unit; moreover he must collect information as to which output units are currently available as well as print-out formats and identifiers of these available output units each time he inputs a data-output command. PA0 5) The user must update the file in the client each time a network environment changes. More precisely, in the above case, the client 8 files an identifier specifying an output unit in relation with a server in the "printcap". For this reason, the user must update the "printcap" with the most recent information as to server-output unit connection to keep the system in order.